In a flywheel assembly having divided type flywheels; a play 12, a torsion spring 13 and a friction member 14 are disposed in series between a first flywheel 10 and a second flywheel 11, and a friction member 15 generating a hysteresis torque TH is connected in parallel, as illustrated in FIG. 7.
In such structure, as illustrated in FIG. 8, the friction member 14 begins to slip at a torque TL when the torsion spring 13 actuates in a torsion angle range beyond a clearance .epsilon. settled by the play 12 to further increase torsion torque. Accordingly, the friction member 15 always works regardless of the clearance .epsilon.. Such type of structure is shown in Japanese, Published Utility Model Application No. 61-23543 and Japanese Published Patent Application No. 61-223348 and are well known prior art structures.
When a large torsion torque is applied at a low-speed region such as starting the flywheel etc. for example, the second flywheel 11 is apt to generate a resonance. It is necessary to enlarge the hysteresis torque TH of the friction member 15 in order to avoid this resonance. However, such enlargement of hysteresis torque TH is restricted from the standpoint of damper performance so that it can not be enlarged so much. Further, the friction member 14, functioning as a breakage prevention mechanism at time of generation of resonance, works only to an extent of the maximum engine torque TEMAX which is a limit of the slip commencing torque TL, and a slippage is always produced between the first flywheel 10 and the second flywheel 11 when a large fluctuation torque exceeding the slip commencing torque TL is applied so that energy can not be transmitted efficiently.